JPH09104014A - Joining method for ceramics injection molded form - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a product having high joining strength with good precision without necessitating or increasing joint working by heating the joint part of two partially molded bodies to make it a softened or molten state and injecting kneaded material between the partially molded bodies and performing molding of this part and mutually joining the partially molded bodies. SOLUTION: A kneaded material consisting of a ceramics powder and an organic binder is injected to the inside (a) of a mold and molded. A partially molded form 1 becoming a part of a molded body 3 is molded and a partially molded body 2 is similarly molded. These partially molded bodies 1, 2 are fitted to a mold for joining as a part of the mold so as to form the molded body 3. The kneaded material is injected to the inside (b) and injection molding of this part is performed and simultaneously the partially molded bodies 1, 2 are joined and unified to finally obtain the molded body 3. In the case of performing injection molding, the end parts 4, 4' containing the joint face of the partially molded bodies 1, 2 are heated at the temperature not lower then the softening temperature of the partially molded bodies 1, 2 and below the boiling point of the organic binder. Therefore, even a molding having a complete shape is easily obtained as the product having high precision without necessitating a complex mold.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for joining a ceramic molded body, and more particularly to a method for joining a molded body injection-molded using a kneaded material of ceramic powder and an organic binder as a material.

[0002]

2. Description of the Related Art Ceramics have excellent properties such as excellent heat resistance and wear resistance, high hardness and good corrosion resistance. In recent years, mechanical parts made of ceramics have been manufactured by utilizing these properties. As a result, high precision parts are required. In molding such ceramics, in general, injection molding has an advantage that a complicated shape can be obtained and processing after injection molding is unnecessary. In addition, the product obtained by injection molding has high strength, excellent mechanical properties, and high dimensional accuracy.

However, there are limits to injection molding,
When obtaining something with a very complicated shape, it is not possible to mold at once, and the molded products are divided and molded separately, and the joining surfaces are melted by heating or by using a solvent. The method of joining is adopted. On the other hand, when the joining method is not used, slip casting using a collapsed core or injection molding using a slide core or the like in a mold is performed.

However, in the case of the method of bonding after molding, since the molded body is pressed and bonded, when the pressing force is constant, the crushing margin is unstable and it is difficult to maintain accuracy, and a collapsed core is used. Also in this case, there is a problem that the dimensional accuracy is not good. As described above, in the conventional method, it was not possible to obtain a product having a high dimensional accuracy, and thus a great deal of labor was required for processing. Further, when a slide core or the like is used for the mold, the structure becomes complicated, and improvement in this is also desired.

[0005]

DISCLOSURE OF THE INVENTION The present invention provides a ceramic product which does not require or has little processing after joining, is highly accurate, and has a high joining strength. An object is to obtain a method for joining injection molded bodies that is useful for manufacturing.

[0006]

According to the present invention, when a molded product obtained by injection-molding a kneaded material composed of ceramic powder and an organic binder is bonded to each other to obtain a product, a joint portion between two molded products is formed. By injecting a kneaded material between the partially molded bodies in a state of being heated and softened or melted, the portion between the partially molded bodies is molded and at the same time the partially molded bodies are joined together. This is a method for joining ceramics injection molded bodies.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Ceramic powders to which the present invention is applied include, for example, MgO, Al ₂ O ₃ and Si.
O ₂ , TiO ₂ , ZrO ₂ , ZnO, Fe ₂ O ₃ , Si
_{O, Si 3 N 4, SiC} , BN, TiC, etc. WC and the like. These ceramic powders may contain metal powder. Examples of the metal powder include metal silicon, Fe, Al, Mg and Ti.

The ceramic powder and the metal powder used in the present invention have been subjected to a crushing process. An apparatus used for pulverization is a ball mill, a stirring mill, a jet mill or the like, and may be either wet pulverization or dry pulverization. Ethyl alcohol, methyl alcohol, other organic solvents, and water are used as the liquid medium when performing wet pulverization. At this time, the particle size after pulverization is not particularly limited,
50 μm is preferred.

On the other hand, the organic binder to be kneaded with this is not particularly limited and can be selected depending on the relationship with the ceramic powder. For example, paraffin wax, microcrystalline wax, oxidized wax, maleated wax, stearic acid. , Oleic acid and the like. Of these, wax-based binders are preferably used. A double-arm pressure kneader, a Banbury mixer, or the like is used as a device for kneading these.

The kneading ratio of the organic binder to the ceramic powder can be appropriately selected, but it is 27-
70% by volume is preferable, and 30 to 60% by volume is particularly preferable. When the kneading ratio is less than 27% by volume, the amount of the organic binder is small, and therefore the viscosity becomes too high, which makes injection molding difficult. On the other hand, when the kneading ratio exceeds 70% by volume, the molded product contains a large amount of the organic binder. Therefore, since the softening is remarkable during the degreasing and the degreasing deformation is large, cracks are easily generated during the degreasing due to the decomposition of the binder, and the degreasing time is remarkably lengthened.

In the method of the present invention, when the molded articles obtained by injection molding are joined together, the kneaded product as described above is injected between the partially molded articles to form a partially molded article. This is to perform injection molding of a portion between the partially molded bodies and simultaneously join the partially molded bodies together.

FIG. 1 shows an example of this step. The product that is finally obtained by joining the partially molded products together is shown in FIG.
It is the molded body 3 of (C). First, the partially molded body 1 which is a part of the product of FIG. 1C is injection-molded. That is, the kneaded material is injection-molded into the inside a of the mold shown in FIG. 1A to injection-mold the partially molded body 1 having a shape of a part of the molded body 3. Similarly, the partially molded body 2 which is a shape of a part of the molded body 3 is injection molded. After that, the obtained partially molded body 1 and partially molded body 2 were used as a part of a mold, as shown in FIG.
As shown in FIG. 3, the molded body 3 is mounted on a joining mold so as to form it. The kneaded material is injected into the inside b of such a mold, and at the same time as the injection molding of this portion, the partial compact 1 and the partial compact 2 are formed.
Are joined and integrated, and finally the joined portion 3 is obtained.
Therefore, the joint portion of the product to be finally obtained is formed of the joint portion 4 of the partial molded body 1 and the joint portion 4 ′ of the partial molded body 12 via the injection molded portion 5.

When the partial molded body 1 and the partial molded body 2 are joined by injection molding, the end portions including the joint surface of the partial molded body (hereinafter referred to as "joint portion") 4, 4'at the time of injection molding. Needs to be heated. The heating temperature at this time is
It is necessary that the softening temperature (Ts) of the partially molded product is not lower than the boiling point of the organic binder, and preferably it is not lower than the melting point of the partially molded product and lower than the temperature of the kneaded product to be newly injection-molded. Good. In addition, the heating width is preferably 0.1 to 10 mm from the joint surface.

Here, the melting point of the partially molded product refers to the peak temperature of the melting endothermic reaction in thermal analysis. In addition, the softening temperature (Ts) of the kneaded material means that the kneaded material that has been a solid transitions from the solid area to the transition area from the solid area to the fluid area through the rubber-like elastic area as the temperature rises. It is the temperature at the transition point to the zone. The softening temperature (Ts) of the kneaded product is usually measured by using a flow tester, which is represented by a change in piston stroke per unit time when a sample is extruded while maintaining a constant cylinder temperature. There are a constant temperature method obtained from the flow rate of each temperature, a temperature increase method obtained from the flow curve showing the change of the piston stroke per unit time at each temperature when the temperature is raised at a constant rate over the test time. . As a method for measuring the boiling point (Tb) of the organic binder, a Beckman boiling point measuring device is used. Here, when the organic binder is composed of two or more kinds of organic components, it is necessary to set the boiling point of the organic component having the lowest boiling point as a reference.

By heating the joint portion in such a temperature range, the joint portion is softened or melted, so that it is well compatible with the kneaded product to be newly injected and firmly integrated. If the heating temperature is lower than the softening temperature of the kneaded product, the bonding with the remaining portion will be insufficient, while if the boiling point of the organic binder or higher, the organic binder will vaporize to generate bubbles in the kneaded product, causing cracking. Cause.

As a method of heating the joint portion of the partial joint portion, a heater for heating the joint portion of the die for integration into which the partially molded body is inserted, hot air, infrared rays, or a heated plate is used. The joint part may be heated directly, or the kneaded material having a relatively high temperature may be injected toward the joint part. The temperature of the kneaded product during injection molding is 70 ° C to 140 ° C.
C. is preferable, and 80 to 120.degree. C. is particularly preferable. When the material temperature is lower than 70 ° C., the fluidity is low and the shape is difficult to be transferred. On the other hand, if the temperature exceeds 140 ° C, burr may occur,
There is a possibility that the partially molded bodies 1 and 2 will be completely melted.

The temperature of the mold during molding is 5 ° C to 6 ° C.
0 degreeC is preferable and 30-55 degreeC is especially preferable. If the temperature of the mold is less than 5 ° C, the cooling rate of each part of the molded body will be different, and as a result, deformation such as warpage or twisting may occur, while if it exceeds 60 ° C, burrs may occur. There is.

The width and shape of the injection-molded joint are preferably such that air entrapment does not easily occur. For example, if the joint surface is uneven, the joint can be made more firmly. The composition of the kneaded product to be injection-molded for bonding may be the same as or different from the partial molded product to be bonded, as long as they are bonded.

The manufacturing method of the present invention is applied to low pressure injection molding. The molding pressure for high-pressure injection molding is 50 kg /
Since it is cm ² or more, in order to prevent the kneaded product from leaking through the gap between the molds, it is necessary to hold down the mold with a high mold clamping force. At this time, if the mold is not accurate,
The mold clamping force may crack the molded product or leak the kneaded product. On the other hand, the molding pressure in the case of low-pressure injection molding is 1 to 10 kg / cm ² , preferably ² to 6 kg / c.
m ² and there is no problem as in the case of high pressure injection molding.
The kneaded material used for low-pressure injection molding has a lower viscosity than the kneaded material used for other molding methods, and is usually 90%.
It is less than 900 PaS at ° C. Therefore, in the case of low-pressure injection molding, a large amount of organic binder is contained in the kneaded product, and it is preferable to carry out the low-pressure injection molding from the viewpoint of the bondability between the partially molded products.

In the present invention, first, the partially molded bodies that are a part of the final product are molded separately. Next, when joining these divided partial compacts, the portion between the joints is newly injection-molded and simultaneously joined with the injection molding, so the positional relationship of the partial compacts is maintained, and the shape accuracy of the joint is improved. There is no problem of deterioration. Therefore, even a molded body having a complicated shape can be divided into a shape that does not have an undercut shape, and thereafter, they can be joined accurately. Further, even a hollow molded body can be easily manufactured.

For example, when manufacturing a hollow product,
A mold as shown in FIG. 2 may be used to separately mold the two-divided molded products and then bond them while molding. FIG. 2A is a cross-sectional view of the hollow final product after joining. In order to manufacture such a product, first, a partial molded body having a shape obtained by removing a joining portion from a portion obtained by dividing the tubular final product into two along the cylinder is obtained by injection molding. 2B and 2C are cross-sectional views of the mold used at this time as seen from two directions. The two partially formed bodies thus obtained are mounted in a joining die as shown in FIG. 2 (D), and joined while being newly injection-molded.

In the conventional method, it was very difficult to produce such a hollow-shaped molded product because the mold could be removed, but it was more liable to crack due to molding shrinkage and the like, but the method of the present invention was used. It can be easily manufactured. INDUSTRIAL APPLICABILITY As described above, the present invention is very useful for producing a molded product having a complicated shape such as an undercut shape or a hollow shape. However, the joining method of the present invention can be applied to any shape and is not limited to these.

A step of removing the organic binder is required from the green molded body thus obtained (hereinafter, removing the organic binder is referred to as "degreasing"). The integrated green molded body is heated in a vacuum to degrease it, and then heated in the atmosphere to burn the residual carbon component and almost completely remove the binder component. When the temperature is raised in a vacuum, the rate of temperature rise is 1 to 20 ° C./hour and 150
When the temperature is raised to ˜300 ° C. and the temperature is raised in the atmosphere, it is preferable to raise the temperature to 450 to 600 ° C. at a temperature rising rate of 20 to 100 ° C./hour.

The molded body degreased in this way is sintered in a nitrogen atmosphere to obtain a sintered body. Sintered 1,70
It is preferable to carry out at 0 to 1,900 ° C. for 2 to 8 hours.

[0025]

The present invention will be described below with reference to examples. Example 1 A kneaded product was prepared by kneading with a dual-arm kneader using the ceramic powder shown in Table 1 and an organic binder mainly composed of wax. The kneaded product contains 45% by volume of binder.

[0026]

[Table 1]

* 1) Ube Industries, Ltd., SN-E10 * 2) Japan Yttrium Co., Ltd. * 3) Sumitomo Chemical Co., Ltd. * 4) Nippon Seiwa Co., Ltd. * 5) Reagent first grade * 6) Made by San Nopco

Using this kneaded product, the mold temperature was 40 ° C., the material temperature was 90 ° C., and the test piece 11 shown in FIG.
And 12 parts were respectively injection molded. The size of each test piece was 32 × 50 × 10t.
Next, the molded products 11 and 12 thus obtained are mounted on a mold for injection bonding which is a part of the mold, and 13 parts are injection-molded while simultaneously molding the molded products 11 and 12. They were integrated to obtain a test piece of 32 × 130 × 10t. At this time, according to the flow curve (FIG. 4) obtained by the temperature raising method using a flow tester (manufactured by Shimadzu Corporation, elevated flow tester) for this kneaded product, the softening temperature (Ts) was 57.2 ° C. Met. In addition, the boiling point of stearic acid, which is the organic component having the lowest boiling point among the organic binders constituting the kneaded product, is 360 ° C. The joint portion 14 'was heated to 70 ° C. by a heater provided in the mold, and the heater was turned off immediately before injection molding the remaining portion 12. The injection molding was performed at a mold temperature of 40 ° C and a material temperature of 10 ° C. Molding pressure is 4 kg in the first 10 seconds
/ Cm ² and hold at 4 kg / cm ² for 20 seconds,
Allowed to solidify.

After the sprue was removed, the molded body 13 obtained by joining was heated to 25 ° C. in vacuum at a temperature rising rate of 5 ° C./hour.
The temperature was raised to 0 ° C. for degreasing, and then the temperature was raised to 500 ° C. at a temperature rising rate of 50 ° C./hour to burn the residual carbon content and almost completely remove the binder component. The molded body degreased in this way is treated with 1,7 in a nitrogen atmosphere.
The test piece was obtained by sintering at 50 ° C. for 4 hours (reference photograph 1).

The joint portion of the test piece thus obtained was apparently very smooth. Four-point bending strength of three test pieces was measured (JIS
R1601), and compared with the strength of the base material collectively molded into a shape of 32 × 130 × 10 t from the beginning. The measurement results are shown in Table 2 and FIG. As can be seen from the table and the figures, the product obtained by the joining method of the present invention has strength equivalent to that of the base material and high joint strength.

[0031]

[Table 2]

[0032]

According to the present invention, a kneaded product is injected between the partial molded bodies to be joined, and the joints of the partial molded bodies are heated to soften or melt this portion. Since they are joined while being molded, the positional relationship of the partially formed bodies is maintained, and high shape accuracy and high joining strength can be obtained. Therefore, even if the molded product has a complicated shape, it is possible to easily obtain a highly accurate product by dividing the molded product, molding it with a simple mold, and then joining the molded product without a complicated mold. Therefore, it is a very useful method for obtaining an undercut shape or a hollow shape, and these can be easily and accurately molded.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing steps of an example of a joining method of the present invention.

FIG. 2 is a schematic cross-sectional view showing the steps of an example of the joining method of the present invention.

FIG. 3 is a schematic perspective view of a test piece manufactured in Example 1.

FIG. 4 is a chart of a flow curve of the kneaded product used in Example 1.

5 is a diagram showing a measurement result of four-point bending strength in Example 1. FIG.

Claims (3)

[Claims] 1. A state in which a joint between two partial compacts is heated to be softened or melted when joining injection-molded partial compacts using a kneaded material composed of ceramic powder and an organic binder as a material to obtain a product. The ceramic injection molding is characterized in that by injecting a kneaded product between the partially molded bodies, the portion between the partially molded bodies is molded and at the same time the partially molded bodies are joined together. How to join the body. 2. Injection molding, molding pressure is 1-10kg /
The method for joining ceramics injection-molded bodies according to claim 1, which is performed by low-pressure injection molding of cm ² . 3. The ceramic injection molded body has a shape having an undercut shape.
Item 6. A method for joining ceramics injection-molded articles as described in the item.